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| United States Patent |
5,595,847
|
|
Nogami
, et al.
|
January 21, 1997
|
Photoconductor having a cured layer of an amino resin-phenol resin
copolycondensate
Abstract
A photoconductor for electrophotography includes an electroconductive
substrate; and a photosensitive layer provided on the electroconductive
substrate and composed of an intermediate layer, a charge generation
layer, and a charge transfer layer laminated in this order, wherein the
intermediate layer is a doped layer and is composed of a cured layer of a
copolycondensate between an amino resin and a phenolic resin hat has been
subjected to doping with at least one dopant.
| Inventors:
|
Nogami; Sumitaka (Kawasaki, JP);
Kitazawa; Michihiro (Kawasaki, JP);
Sato; Katsuhiro (Kawasaki, JP)
|
| Assignee:
|
Fuji Electric Co., Ltd. (Kanagawa, JP)
|
| Appl. No.:
|
361331 |
| Filed:
|
December 21, 1994 |
Foreign Application Priority Data
| Current U.S. Class: |
430/64 |
| Intern'l Class: |
G03G 005/14 |
| Field of Search: |
430/60,64,65
|
References Cited
U.S. Patent Documents
| 3861921 | Jan., 1975 | Hottmann et al. | 430/275.
|
| 4800144 | Jan., 1989 | Ueda et al. | 430/58.
|
| 5173385 | Dec., 1992 | Nozomi et al. | 430/60.
|
| Foreign Patent Documents |
| 4411732 | Oct., 1994 | DE.
| |
| 57-81269 | May., 1982 | JP.
| |
| 59-93453 | May., 1984 | JP.
| |
| 60-32054 | Feb., 1985 | JP.
| |
| 60-111255 | Jun., 1985 | JP.
| |
| 61-110153 | May., 1986 | JP.
| |
| 63-116160 | May., 1988 | JP.
| |
| 63-116161 | May., 1988 | JP.
| |
| 63-116162 | May., 1988 | JP.
| |
Primary Examiner: Goodrow; John
Attorney, Agent or Firm: Spencer & Frank
Claims
What is claimed is:
1. A photoconductor for electrophotography, comprising:
an electroconductive substrate; and
a photosensitive layer provided on the electroconductive substrate and
comprised of an intermediate layer, a charge generation layer, and a
charge transfer layer laminated in this order,
wherein the intermediate layer is a doped layer and is comprised of a cured
layer of a copolycondensate between an amino resin and a phenolic resin
that has been subjected to doping with at least one dopant.
2. The photoconductor for electrophotography as claimed in claim 1, wherein
the amino resin is at least one amino resin selected from the group
consisting of melamine resins, urea resins and benzoguanamine resins.
3. The photoconductor for electrophotography as claimed in claim 1, wherein
the phenolic resin is a phenolic resin derived from resol.
4. The photoconductor for electrophotography as claimed in claim 1, wherein
the phenolic resin is a condensate between furfural and formalin.
5. The photoconductor for electrophotography as claimed in claim 1, wherein
the intermediate layer is doped with at least one dopant selected from the
group consisting of halogen-derived substances and sulfonic acid
compounds.
6. The photoconductor for electrophotography as claimed in claim 5, wherein
the at least one dopant is iodine.
7. The photoconductor for electrophotography as claimed in claim 5, wherein
the at least one dopant is an organic sulfonic acid.
8. The photoconductor for electrophotography as claimed in claim 7, wherein
the organic sulfonic acid is .alpha.-naphthalenesulfonic acid.
9. The photoconductor for electrophotography as claimed in claim 7, wherein
the organic sulfonic acid is p-toluenesulfonic acid.
10. The photoconductor for electrophotography as claimed in claim 1,
wherein the phenolic resin is present in an amount ranging from 10 to 50
parts by weight with respect to 100 parts by weight of the amino resin.
11. The photoconductor for electrophotography as claimed in claim 6,
wherein the iodine is present in an amount ranging from 4 to 10% by weight
based on total resin content.
12. The photoconductor for electrophotography as claimed in claim 8,
wherein the .alpha.-naphthalenesulfonic acid is present in an amount
ranging from 2 to 50% by weight based on total resin content.
13. The photoconductor for electrophotography as claimed in claim 9,
wherein the p-toluenesulfonic acid is present in an amount ranging from 10
to 40% by weight based on total resin content.
14. The photoconductor for electrophotography as claimed in claim 1,
wherein the intermediate layer further comprises a powder selected from
the group consisting of titanium oxide, zinc oxide, silica, kaolin,
calcium carbonate, and fine plastic particles.
15. The photoconductor for electrophotography as claimed in claim 1,
wherein the intermediate layer has a thickness ranging from 0.2 to 20
.mu.m.
16. The photoconductor for electrophotography as claimed in claim 1,
wherein the intermediate layer is prepared by a process comprising:
coating a coating solution comprising the amino resin, the phenolic resin,
the at least one dopant and a solvent onto the electroconductive substrate
to provide a coating;
drying the coating to provide a dried coating; and
curing the dried coating.
17. The photoconductor for electrophotography as claimed in claim 16,
wherein the dried coating is cured at a temperature ranging from
80.degree. to 150.degree. C. for a time ranging from 60 to 15 minutes.
18. The photoconductor for electrophotography as claimed in claim 16,
wherein the amino resin and the at least one dopant form a charge transfer
complex within the coating solution.
19. The photoconductor for electrophotography as claimed in claim 1,
wherein the intermediate layer consists essentially of the cured layer of
a copolycondensate between an amino resin and a phenolic resin, and
wherein the at least one dopant is at least one electron attractive
compound.
20. The photoconductor for electrophotography as claimed in claim 19,
wherein the at least one electron attractive compound comprises at least
one compound selected from the group consisting of halogen-derived
substances and sulfonic acid compounds.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic photoconductors for
electrophotography, and more specifically, to a photoconductor for
electrophotography which has an intermediate layer.
2. Description of the Prior Art
A photoconductor for electrophotography (hereinafter referred to as a
photoconductor) basically comprises a photosensitive layer on a conductive
substrate. Generally, however, it has an intermediate layer in order to
improve adhesion between the conductive substrate and the photosensitive
layer, to inhibit charge injection from the conductive substrate into the
photosensitive layer, and to cover defects in the surface of the
conductive substrate.
As such an intermediate layer of an inorganic type is known an Alumite
layer. Japanese Patent Application Laying-open Nos. 116,160/1988,
116,161/1988 and 116,162/1988, and U.S. Pat. No. 4,800,144, for example,
disclose that an Alumite layer with a thickness of several micrometers
provided on an aluminum substrate is a layer having stable barrier
characteristics which inhibit the injection of charges from the conductive
substrate into the photosensitive layer without undergoing little
influence from environmental changes.
As organic materials for the intermediate layer have hitherto been known
polyvinyl alcohol, casein, and alcohol-soluble nylon.
The characteristics required of the intermediate layer include the ability
to upgrade image quality by enhancing adhesion between the photosensitive
layer and the conductive substrate, and improving the applicability of the
photosensitive layer onto the conductive substrate by covering the surface
defects of the conductive substrate. The characteristics required first of
all are satisfactory electrical characteristics for a photoconductor,
namely, high sensitivity and low residual potential. To achieve these
desired characteristics, the above-mentioned intermediate layer of the
organic type generally is made of a resin having low resistance itself.
This type of intermediate layer is also required to have electrical
characteristics unaffected by the environment. However, most of
intermediate layers from the aforementioned organic materials are apt to
be affected easily by environmental factors, especially humidity. Under
low-humidity conditions, their resistance becomes high, causing fog to the
resulting image. At high humidity, their resistance becomes too low, and
charge potential lowers, decreasing image density. Thus, the intermediate
layer using such resin is generally coated with a very small thickness of,
say, 0.1 to 1 .mu.m. Such a thin film, needless to say, has a low effect
of covering the defects present in the conductive substrate.
To overcome the above drawbacks, an organic type intermediate layer which
functions fully even with a large thickness is under energetic
development. For instance, Japanese Patent Application Publication Nos.
42,498/1987, 19,869/1988, 51,183/1989, 51,185/1989 and 60,177/1990
exemplify intermediate layers with a large thickness having a conductive
fine powder dispersed in various resins. The electric conduction of these
exemplified intermediate layers is attributed to electronic conduction by
the conductive fine powder. Hence, even though they have a large
thickness, they are assumed to show satisfactory electrical conductivity
and undergo minimal influence from temperature and humidity. However, the
dispersions of the conductive fine powder are subject to the precipitation
or agglutination of the conductive fine powder, thus requiring careful
administration of the dispersions. Furthermore, a considerable amount of
the conductive fine powder has to be incorporated in the coating with the
aim of imparting sufficient conductivity. As a result, the surface
smoothness of the intermediate layer vanishes, and the injection of
charges from the intermediate layer into the photosensitive layer is apt
to occur easily. In order to give smoothness to the intermediate layer,
there is further need to provide a thin layer of a resin, such as nylon or
casein, onto it.
According to the above-described prior art, the intermediate layer
particularly of the organic type must be able to upgrade image quality
based on the improvement of adhesion between the photosensitive layer and
the conductive substrate, and the improvement of the applicability of the
photosensitive layer onto the conductive substrate by covering the surface
defects of the conductive substrate. To fulfill this requirement, there
has been proposed a method which comprises dispersing a conductive fine
powder in various resins to form intermediate layers with a large
thickness. However, dispersions of the conductive fine powder are subject
to the precipitation or agglutination of the conductive fine powder, thus
posing difficulty with the administration of the dispersions, and
involving viscosity changes due to coagulation. Consequently, the surface
smoothness of the intermediate layer disappears, thus arousing a new
problem that a thin layer of a resin must be provided on the intermediate
layer.
SUMMARY OF THE INVENTION
An object of this invention is to provide a photoconductor for
electrophotography having a novel organic intermediate layer.
Another object of the invention is to provide a photoconductor for
electrophotography having an intermediate layer which is free from a
conductive fine powder and on which a thin layer of a resin need not be
provided.
Still another object of the invention is to provide a photoconductor for
electrophotography having an intermediate layer which is so stable as to
undergo no influence from the environment and which ensures good adhesion
between a photosensitive layer and a conductive substrate.
In an aspect of the present invention, there is provided a photoconductor
for electrophotography comprising a photosensitive layer on a conductive
substrate, the photosensitive layer comprising at least an intermediate
layer, a charge generation layer, and a charge transfer layer laminated in
this order, wherein
the intermediate layer comprises a cured layer of the copolycondensate
between an amino resin and a phenolic resin that has been subjected to
doping.
Here, the amino resin may be at least one member selected from the group
consisting of melamine resins, urea resins and benzoguanamine resins.
The phenolic resin may be a resol type phenolic resin.
The phenolic resin may be the condensate between furfural and formalin.
The doping may be performed using at least one dopant selected from the
group consisting of halogen-derived substances and sulfonic acid
compounds.
The dopant may be iodine.
The dopant may be an organic sulfonic acid.
The organic sulfonic acid may be .alpha.-naphthalenesulfonic acid.
The organic sulfonic acid may be p-toluenesulfonic acid.
The amino resin and the phenolic resin may be in such proportions that the
amount of the phenolic resin is 10 to 50 parts by weight with respect to
100 parts by weight of the amino resin.
The proportion of the iodine may be 4 to 10% by weight based on the total
resin content.
The proportion of the .alpha.-naphthalenesulfonic acid may be 2 to 50% by
weight based on the total resin content.
The proportion of the p-toluenesulfonic acid may be 10 to 40% by weight
based on the total resin content.
The intermediate layer may further contain a powder selected from the group
consisting of titanium oxide, zinc oxide, silica, kaolin, calcium
carbonate, and fine plastic particles.
The thickness of the intermediate layer may be 0.2 to 20 .mu.m.
The intermediate layer may be prepared by coating a coating solution
comprising the amino resin, the phenolic resin, the dopant and a solvent,
drying the coating, and curing the dried coating.
The curing conditions may be from 80.degree. to 150.degree. C. and from 60
to 15 minutes.
It has been unknown that an amino resin forms a charge transfer complex
with iodine or an organic sulfonic acid, giving markedly improved
electrical conductivity. However, when the amino resin doped with iodine
or organic sulfonic acids is used as an intermediate layer of a
photoconductor for electrophotography, the resulting intermediate layer
masks the defects of the conductive substrate and imparts excellent
electriscal characteristics. It has also been found that when the doped
amino resin is copolycondensed with a phenolic resin, its adhesion with
the conductive substrate is markedly improved, and that even if left to
stand under high-temperature, high-humidity conditions, for instance, the
copolycondensate does not show any changes in its characteristics.
The above and other objects, effects, features and advantages of the
present invention will become more apparent from the following description
of embodiments thereof taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional structural view showing a photoconductor according to
an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in more detailed by
embodiments. However, the present invention should not be contoured as
being limited thereto.
The construction of the present invention will be described in detail. The
conductive substrate in this invention is a cylinder, a film or a sheet of
a metal, or a polymer, earthenware, glass, wood or paper that has been
treated to have conductivity. On the conductive substrate is to be
provided a cured film of the copolycondensate of an amino resin and a
phenolic resin that has been doped, the cured film being relevant to the
present invention. As the dopant for the cured film of the
copolycondensate of the amino resin and the phenolic resin, there can be
used iodine, iron chloride, and sulfonic acid compounds, especially,
iodine and aromatic sulfonic acids such as naphthalenesulfonic acid or
p-toluenesulfonic acid. The method of forming the cured film comprises
dissolving the amino resin and the phenolic resin in a solvent, adding the
dopant to the solution, coating the mixture onto the conductive substrate,
drying the coating, and then heating it for curing.
The amino resin for use in the invention is a condensation product prepared
by reacting an amino compound, such as urea, melamine, acetoguanamine or
benzoguanamine, with an aldehyde compound, such as formaldehyde,
acetaldehyde, butyraldehyde, furfural, or acrolein, to introduce an
alkylol, and etherifying the product with an alcohol. Any of the so
prepared amino resins may be used alone or as a copolycondensate. Such
amino resins are generally called urea resins, melamine resins, or
benzoguanamine resins. Phenolic resins to be copolycondensed with these
amino resins during the curing reaction are preferably resol type resins
obtained by condensing phenols and aldehydes in the presence of alkaline
catalysts. The phenols used are phenol, cresol, xylenol, and alkylphenols
such as p-tert-butylphenol or p-tert-amylphenol. The aldehydes used are
formaldehyde, paraformaldehyde, acetaldehyde, butyraldehyde, and furfural.
Those amino resins and phenolic resins are easily available as the starting
resins for paints. Examples of the amino resins known include UBAN 10S,
UBAN 20HS, UBAN 2020, UBAN 134, UBAN 2060 and UBAN 91-55 produced by
Mitsui Toatsu Chemicals, Inc., and SUPERBEWCAMINE L-806-60, L-145-60 and
TD-126 produced by Dainippon Ink and Chemicals, Inc. Examples of the
phenolic resins known include PRIOPHEN 5010, PRIOPHEN 5030, PRIOPHEN
TD-447, and SUPERBECCACITE 1001 produced by Dainippon Ink and Chemicals,
Inc.
The mixing ratio for the amino resin and the phenolic resin before curing
and copolycondensation is preferably 10 to 50 parts by weight of the
phenolic resin with respect to 100 parts by weight of the amino resin. Its
proportion less than 10 parts by weight is not preferred, because the
adhesion of the intermediate layer to the conductive substrate, e.g. an
aluminum cylinder, and its adhesion to the photosensitive layer to be
applied thereon become poor. The proportion of more than 50 parts by
weight results in a low doping effect, which in turn leads to
unsatisfactory photoconductors characteristics.
The photoconductors of the present invention is a cured film of the
copolycondensate between the amino resin and the phenolic resin that has
been doped. Examples of the dopant usable are electron attractive
compounds, such as halogen substances or sulfonic acid compounds, which
will form charge transfer complexes with amino resins. The suitable
examples for the present invention are iodine, aromatic sulfonic acid,
such as p-toluenesulfonic acid and 2-naphthalenesulfonic acid. The amount
of the dopant added is 4 to 10% by weight of iodine based on the total
amount of the resins, 10 to 40% by weight of p-toluenesulfonic acid based
thereon, or 20 to 50% by weight of 2-naphthalenesulfonic acid
(.alpha.-naphthalenesulfonic acid). The dopant and the above resins are
used as a coating solution, and dissolved with a suitable solvent, such as
methanol, ethanol, tetrahydrofuran, 2-methoxyethyl alcohol, 2-ethoxyethyl
alcohol, or ethylene glycol dimethyl ether, before being coated. The
coating applied is heated for 10 to 30 minutes at 120.degree. to
150.degree. C. so as to be cured.
In order to prevent the occurrence of a moire ascribed to light returning
from the conductive substrate, the intermediate layer of the present
invention may have titanium oxide, zinc oxide, silica, kaolin, calcium
carbonate, or fine particles of plastic added, and may have an antioxidant
or a leveling agent further added.
By so providing the intermediate layer on the conductive substrate and a
photosensitive layer on the intermediate layer, a photoconductor can be
produced. The photosensitive layer is available in any form, such as a
single-layer type photosensitive layer prepared by coating a solution
containing a charge generating agent and a charge transfer agent dissolved
and dispersed in a resin; a positively charged laminate type
photosensitive layer prepared by providing a charge transfer layer, a
charge generation layer, and if desired, a conductive layer, in this
order; or a negatively charged laminate type photosensitive layer prepared
by providing a charge generation layer and a charge transfer layer in this
order. The intermediate layer of the present invention is obtained as a
smooth, uniform coating even when coated with a large thickness of several
tens of micrometers. Thus, it can cover surface defects attributed to
scars, dirt or uneven cuts of the conductive substrate that have mainly
contributed to decreasing the rate of non-defectives among
photoconductors. Particularly with the negatively charged laminate type
photosensitive layer, the charge generation layer needs to be coated on
the conductive substrate to a very small thickness, say, of 0.01 to 1.0
.mu.m. Thus, the decrease in the rate of non-defectives due to the surface
defects of the conductive substrate has posed a major problem. Under these
circumstances, the present invention is a particularly effective means as
an intermediate layer of a negatively charged laminate type
photoconductors comprising a charge generation layer and a charge transfer
layer provided in this order on a conductive substrate.
Of the components of the photosensitive layer to be provided on the
intermediate layer, the charge generation layer is formed by dispersing a
known organic pigment, such as a phthalocyanine pigment, an anthanthrone
pigment, a perylene pigment, a perinone pigment, an azo pigment, or a
disazo pigment, in a resin, such as polyester, polycarbonate, polyvinyl
butyral, polyvinyl acetate, polyvinyl chloride, or acrylic resin. The
charge transfer layer to be provided on the charge generation layer is
formed by dissolving an enamine compound, a hydrazone compound, a styryl
compound, or an amine compound in a suitable solvent together with a
film-forming binder compatible with any of such compounds, such as
polycarbonate, polyester, polystyrene or- styrene copolymer, coating the
solution, and drying the coating. The preferred thickness of the charge
transfer layer is 5 to 50 .mu.m.
As set forth above, the intermediate layer of the present invention is
formed by dissolving the amino resin and the phenolic resin in a solvent,
adding the dopant to the solution, coating the mixture onto the conductive
substrate, drying the coating, and then heating and curing it. The
thickness of the intermediate layer after drying is 0.1 to 30 .mu.m,
preferably 0.5 to 20 .mu.m. If it is less than 0.1 .mu.m, it is difficult
to mask the defects of the conductive substrate. The thickness greater
than 30 .mu.m is not preferred, because the residual potential becomes
high. The conditions for heating and curing may be those in customary use,
say, 60 to 15 minutes at 80.degree. to 150.degree. C., preferably 40 to 20
minutes at 100.degree. to 140.degree. C.
The present invention will now be illustrated in greater detail with
reference to the following examples based on FIG. 1. FIG. 1 is a sectional
structural view showing a photoconductor relevant to an embodiment of the
invention.
The photoconductor comprises a photosensitive layer on a conductive
substrate, the photosensitive layer 5 comprising an intermediate layer 2,
a charge generation layer 3, and a charge transfer layer 4 laminated in
this order.
A crude aluminum pipe measuring .phi.30.times.260.5 L (mm) was prepared as
the conductive substrate 1. Its surface was measured for the degree of
roughness, which was found to be a maximum of 7.3 .mu.m. Then, a melamine
resin (UBAN 20SB, a product of Mitsui Toatsu Chemicals, Inc.) was used as
an amino resin to prepare coating solutions as shown in Table 1. Each of
the coating solutions was dip-coated onto the crude aluminum pipe so that
its thickness after drying would be 20 .mu.m. The coating applied was
baked for 20 minutes at 140.degree. C. so as to be cured, thereby forming
the intermediate layer 2.
Then, the intermediate layer 2 was dip-coated with a coating solution
prepared by dispersing 1 part by weight of X type metal-free
phthalocyanine (FASTGEN BLUE 8120B, a product of Dainippon Ink and
Chemicals, Inc.) and 1 part by weight of a polyvinyl acetal resin (S-LEC,
a product of Sekisui Chemical Co., Ltd.) together with methylene chloride
by means of a paint shaker. Thus was formed the charge generation layer 3
with a thickness after drying of 0.2 .mu.m. Onto the charge generation
layer 3 was dip-coated a coating solution prepared by dissolving 10 parts
by weight of a polycarbonate resin (UPIRON PCZ-300, a product of
Mitsubishi Gas Chemical Co., Inc.) and 10 parts by weight of
N,N-diethylaminobenzaldehyde diphenylhydrazone in 80 parts by weight of
tetrahydrofuran. Thus was formed the charge transfer layer 4 with a
thickness after drying of 20 .mu.m. This way, a photoconductor was
completed.
TABLE 1
__________________________________________________________________________
Coating Curing Solids
solution
Dopant
Resin added
agent Filler Solvent
content
__________________________________________________________________________
a Iodine (4)
PHENOLITE
-- Titanium
Ethanol
30%
5030 (20) oxide TTO-
(Dainippon 55(S) (50)
Ink and (Ishihara
Chemicals) Sangyo)
b Iodine (4)
SUPERB- -- -- Methanol
25%
CCACITE
1001 (20)
(Dainippon
Ink and
Chemicals)
c Ammonium
HITAFURAN
-- Spherical
Tetrahy-
20%
naphtha-
VF-302 (20) silica drofuran
lene-2-
(Hitachi ADMAFINE
sulfonate
Kasei S0C2 (30)
(20) Kogyo) (Tatsumori)
d Ammonium
BECCOSOL
-- -- Ethanol
20%
naphtha-
1308 (20)
lene-2-
(Dainippon
sulfonate
Ink and
(30) Chemicals)
e Iodine (6)
-- Trimellitic
-- Ethanol
24%
anhydride
(4)
f Iodine (6)
-- Ammonium
-- Ethanol
23%
benzoate
(6)
g p-toluene-
-- Mesaconic Ethanol
21%
sulfonic anhydride
acid (20) (6)
__________________________________________________________________________
Notes:
For the coating solutions in the table, figures in the parentheses
represent the amounts (parts by weight) of the resins and the additives
incorporated as solids based on 100 parts by weight of the melamine resin
as solids.
The so produced photoconductors having the intermediate layer 2 obtained
from the coating solutions a, b and c were designated as Examples 1, 2 and
3, respectively. Those having the intermediate layer 2 obtained from the
coating solutions d, e, f and g were designated as Comparative Examples 1,
2, 3 and 4, respectively. These photoconductors were each evaluated for
the stability of the coating solution, and the adhesion of the
photoconductors under normal temperature, normal humidity conditions
(25.degree. C. 50 RH %) (hereinafter referred to as N/N) and high
temperature, high humidity conditions (60.degree. C. 90 RH %) (hereinafter
referred to as H/H). The results are shown in Table 2.
TABLE 2
______________________________________
Stability of
coating Adhesion
solution N/N Adhesion H/H
______________________________________
Example 1 No abnormality
Good Good
after 2 weeks
Example 2 No abnormality
Good Good
after 2 weeks
Example 3 No abnormality
Good Good
after 2 weeks
Comparative
No abnormality
Good Miliary blister
Example 1 after 1 month developed in 2
days
Comparative
Viscosity Good Miliary blister
Example 2 increased in developed in
3 days 1 day
Comparative
No abnormality
Good Miliary blister
Example 3 after 2 weeks developed in
2 days
Comparative
Viscosity Good Miliary blister
Example 4 increased in developed in
1 week 1 day
______________________________________
In all of Examples 1 to 3, satisfactory results were obtained. In
Comparative Examples 1 to 4, a miliary blister developed in a short time,
particularly in regard to the adhesion H/H, demonstrating that the
photoconductors of these comparative examples were unusable.
Next, the above photoconductors were each mounted on a laser printer (LASER
JET-2, a product of Hewlett Packard), and evaluated for the image quality
in the N/N environment (25.degree. C. 50 RH %) and the H/H environment
(60.degree. C. 85 RH %). The results are shown in Table 3.
TABLE 3
______________________________________
N/N H/H
environment environment
______________________________________
Example 1 Good Good
Example 2 Moire occurred
Moire occurred
Example 3 Moire occurred
Moire occurred
Comparative Moire occurred
Fog occurred
Example 1
Comparative Moire occurred
Fog occurred
Example 2
Comparative Moire occurred
Fog occurred
Example 3
Comparative Moire occurred
Fog occurred
Example 4
______________________________________
As shown in Table 3, the photoconductors of Comparative Examples 1 to 4
posed the problem of a fog occurring in the resulting image in the H/H
environment, while the photoconductors of Examples 1 to 3 caused no fog in
the same environment.
According to the present invention, as described above, the amino resin
forms a charge transfer complex with iodine or an organic sulfonic acid,
thereby markedly improving electrical conductivity as demonstrated in the
Examples. Its use as an intermediate layer for an electrophotographic
photoconductors, therefore, can mask the defects of the conductive
substrate and impart excellent electrical characteristics. Its
copolycondensation with a phenolic resin has been found to improve the
adhesion of the photosensitive layer to the conductive substrate
remarkably, and to enable the photoconductors to show no changes in the
characteristics even when left to stand under high temperature and high
humidity conditions.
The present invention has been described in detail with respect to
preferred embodiments, and it will now be that changes and modifications
may be made without departing from the invention in its broader aspects,
and it is the intention, therefore, in the appended claims to cover all
such changes and modifications as fall within the true spirit of the
invention.
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